Recently, electronic apparatuses such as a server and a supercomputer have been actively developed to achieve higher performance. Electronic components mounted in electronic apparatuses such as a central processing unit (CPU) generate heat during operation.
If the electronic components such as a CPU are overheated, deficiencies such as a breakdown, a malfunction, or deterioration in processing performance may occur. Thus, a cooler is provided to cool the electronic component that generates a large amount of heat.
Air cooling or liquid cooling is used to cool the electronic components. The liquid cooling is most likely to be employed to cool the electronic component that generates a large amount of heat. Such technique is described in Japanese Laid-open Patent Publication Nos. 2006-19595 and 11-163565. Hereinafter, the components that generate a large amount of heat are referred to as heat generating components.
In a cooling system of liquid cooling type, a heat receiving portion is mounted on the heat generating component and a heat dissipater such as a heat exchanger is disposed remote from the heat generating component. The heat receiving portion and the heat dissipater are connected by a pipe or a tube (hereinafter, simply referred to as a pipe). The heat receiving portion has a channel through which a coolant flows. Circulation of the coolant between the heat receiving portion and the heat dissipater allows the heat generated at the heat generating component to be transferred to the heat dissipater and to be dissipated into the atmosphere from the heat dissipater.
In this application, water or other liquids (refrigerant) for transferring the heat from the heat receiving portion to the heat dissipater is referred to as a coolant.
Wiring boards used in electronic apparatuses such as the servers and the supercomputers are likely to have the heat generating component on each surface thereof. In such a wiring board, the heat receiving portion is disposed on each surface of the heat generating component. Pipes are arranged to allow the coolant to sequentially pass the heat receiving portions or pipes are branched by branch joints to allow the coolant to pass in parallel through the heat receiving portions.